Jetty 12.1.6 ResourceHandler not respecting start of byte range request when setUseFileMapping is true

[sandhu]

Jetty version(s)
12.1.6, but fails as far back as 12.1.4

Jetty Environment
jetty-12 only

HTTP version
Tested on http2

Java version/vendor (use: java -version)
Java 21 and 25

OS type/version
OSX: Darwin Kernel Version 25.2.0 on Apple Silicon

Description
When using the Resource Handler to serve up static assets and setUseFileMapping is true, requests with a byte range not starting at 0, e.g., range: "bytes=15032-49184", the server attempts to send the bytes starting from 0 resulting in a java.io.IOException: written 49185 > 34153 content-length

Requesting a byte range starting at 0, works as expected.

Setting setUseFileMapping to false resolves the issue.

How to reproduce?
Use a ResourceHandler to server up static assets and setUseFileMapping to true. Then request a byte range not starting at 0.

[lorban]

I tried reproducing your issue but I could not.

With the following setup:

Server server = new Server(8080);
ResourceHandler handler = new ResourceHandler();
handler.setUseFileMapping(true);
handler.setBaseResource(ResourceFactory.of(server).newResource(Path.of("/some/existing/path/")));
server.setHandler(handler);
server.start();

the following command:

curl -H 'range: bytes=100-200' http://localhost:8080/existing-file.txt

actually serves the requested byte range.

If you could post a reproducer that we can run, we could help you figuring out where the problem is.

[sandhu]

Thank you for looking into it.

I've managed to narrow the issue down to a range request starting at a non-zero offset for a large binary file. My use case is a pmtiles file downloadable from https://maps.protomaps.com/builds/

I have 24G allocated to the JVM.

IIRC large files with setUseFileMapping worked fine in Jetty 12.0.x, but have stopped working in 12.1.x.

[lorban]

As far as I can tell, mapped files work fine both for jetty 12.0 and 12.1. Again, if you encounter a problem, we'd be happy to look into it, if we can reproduce it.

BTW, did you notice that setUseFileMapping() got deprecated and replaced with setMinMappedFileSize() in 12.1?

[sandhu]

The code is inside a fairly large clojure project that I upgraded from 12.0.x to 12.1.x when I started seeing the issue. Not sure if the following exception stacktrace helps.

java.io.IOException: written 201 > 97 content-length
	at org.eclipse.jetty.server.internal.HttpChannelState$ChannelResponse.write(HttpChannelState.java:1381)
	at org.eclipse.jetty.server.Response$Wrapper.write(Response.java:839)
	at org.eclipse.jetty.server.handler.ContextResponse.write(ContextResponse.java:56)
	at org.eclipse.jetty.http.content.FileMappingHttpContentFactory$MultiBufferFileMappedHttpContent$1.process(FileMappingHttpContentFactory.java:201)
	at org.eclipse.jetty.util.IteratingCallback.processing(IteratingCallback.java:377)
	at org.eclipse.jetty.util.IteratingCallback.iterate(IteratingCallback.java:354)
	at org.eclipse.jetty.http.content.FileMappingHttpContentFactory$MultiBufferFileMappedHttpContent.writeTo(FileMappingHttpContentFactory.java:204)
	at org.eclipse.jetty.http.content.HttpContent$Wrapper.writeTo(HttpContent.java:250)
	at org.eclipse.jetty.server.ResourceService.sendData(ResourceService.java:706)
	at org.eclipse.jetty.server.ResourceService.doGet(ResourceService.java:207)
	at org.eclipse.jetty.server.handler.ResourceHandler.handle(ResourceHandler.java:196)
	at org.eclipse.jetty.server.handler.ContextHandler.handle(ContextHandler.java:1224)
	at org.eclipse.jetty.server.Handler$Sequence.handle(Handler.java:859)
	at org.eclipse.jetty.server.Server.handle(Server.java:197)
	at org.eclipse.jetty.server.internal.HttpChannelState$HandlerInvoker.run(HttpChannelState.java:787)
	at org.eclipse.jetty.server.internal.HttpConnection.onFillable(HttpConnection.java:410)
	at org.eclipse.jetty.server.internal.HttpConnection$FillableCallback.succeeded(HttpConnection.java:1805)
	at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:105)
	at org.eclipse.jetty.io.ssl.SslConnection$SslEndPoint.onFillable(SslConnection.java:614)
	at org.eclipse.jetty.io.ssl.SslConnection.onFillable(SslConnection.java:415)
	at org.eclipse.jetty.io.ssl.SslConnection$2.succeeded(SslConnection.java:156)
	at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:105)

I'll try and create a minimal example to reproduce the issue.

[joakime]

What specific JVM are you using? (the results of java --version please).
This might be reproducible on an identical JVM as yours.

[sandhu]

I've tried with 21 and 25. Both fail for me with large binary files.

openjdk 21.0.10 2026-01-20
OpenJDK Runtime Environment Homebrew (build 21.0.10)
OpenJDK 64-Bit Server VM Homebrew (build 21.0.10, mixed mode, sharing)

and

openjdk 25.0.2 2026-01-20
OpenJDK Runtime Environment Homebrew (build 25.0.2)
OpenJDK 64-Bit Server VM Homebrew (build 25.0.2, mixed mode, sharing)

Both running on Apple Silicon.